The present invention relates generally to the coupling of selected input and output lines or channels through which optical signals are directed, and to the routing of optical signals to and from such lines or channels. More specifically, the present invention relates to the design and use of a device adapted to effect selection and coupling through coordinated mechanical indexing movements. Such a device provides advantage in a wide variety of fields of application, particularly in applications involving the generation and transmission of analytical information. Specific fields of use include the preparation, sampling and analyzing of soluble materials as well as the testing of other fluids and solid materials exhibiting optical characteristics.
Optical transport techniques are often utilized to direct a beam or pulse of light from a light source to a test site and, subsequently, to carry analytical information generated or measured at the test site to a suitable light receiving device. Analytical information transmitted by optical means can be chemical or biological in nature. For example, the analytical information can be used to identify a particular analyte, i.e., a component of interest, that is resident within the sample contained at the test site and to determine the concentration of the analyte. Examples of analytical signals include, among others, emission, absorption, scattering, refraction, and diffraction of electromagnetic radiation over differing ranges of spectra. Many of these analytical signals are measured through spectroscopic techniques. Spectroscopy generally involves irradiating a sample with some form of electromagnetic radiation (i.e., light), measuring an ensuing consequence of the irradiation (e.g., absorption, emission, or scattering), and interpreting of the measured parameters to provide the desired information. An example of an instrumental method of spectroscopy entails the operation of a spectrophotometer, in which a light source in combination with the irradiated sample serves as the analytical signal generator and the analytical signal is generated in the form of an attenuated light beam. The attenuated signal is received by a suitable input transducer such as a photocell. The transduced signal, such as electrical current, is then sent to a readout device.
As one example for implementing spectral analysis, a spectrophotometer uses ultraviolet (UV) and/or visible light, or in other cases infrared (IR) or near infrared (NIR) light, to scan the sample and calculate absorbance values. In one specific method involving the UV or UV-visible spectrophotometer, the UV sipper method, the sample is transferred to a sample cell contained within the spectrophotometer, is scanned while residing in the sample cell, and preferably is then returned to the test vessel.
The concentration of a given analyte in a sample through spectrochemical determination typically involves several steps. These steps can include (1) acquiring an initial sample; (2) performing sample preparation and/or treatment to produce the analytical sample; (3) using a sample introduction system to present the analytical sample to the sample holding portion of a selected analytical instrument (e.g., transferring the sample to the sample-holding portion of a UV spectrophotometer); (4) measuring an analytical signal (e.g., an optical signal) derived from the analytical sample; (5) establishing a calibration function through the use of standards and calculations; (6) interpreting the analytical signal based on sample and reference measurements; and (7) feeding the interpreted signal to a readout and/or recording system.
Conventional equipment employed in carrying out the above processes are generally known in various forms. Measurement of the analytical signal involves employing a suitable spectrochemical encoding system to encode the chemical information associated with the sample, such as concentration, in the form of an optical signal. In spectrochemical systems, the encoding process entails passing a beam of light through the sample under controlled conditions, in which case the desired chemical information is encoded as the magnitude of optical signals at particular wavelengths. Measurement and encoding can occur in or at sample cells, cuvettes, tanks, pipes, solid sample holders, or flow cells of various designs.
In addition, a suitable optical information selector is typically used to sort out or discriminate the desired optical signal from the several potentially interfering signals produced by the encoding process. For instance, a wavelength selector can be used to discriminate on the basis of wavelength, or optical frequency. A radiation transducer or photodetector is then activated to convert the optical signal into a corresponding electrical signal suitable for processing by the electronic circuitry normally integrated into the analytical equipment. A readout device provides human-readable numerical data, the values of which are proportional to the processed electrical signals.
For spectrophotometers operating according to UV-visible molecular absorption methods, the quantity measured from a sample is the magnitude of the radiant power or flux supplied from a radiation source that is absorbed by the analyte species of the sample. Ideally, a value for the absorbance A can be validly calculated from Beer""s law:       A    =                            -          log                ⁢                  xe2x80x83                ⁢        T            =                                    -            log                    ⁢                      xe2x80x83                    ⁢                      P                          P              0                                      =        abc              ,
where T is the transmittance, P0 is the magnitude of the radiant power incident on the sample, P is the magnitude of the diminished (or attenuated) radiant power transmitted from the sample, a is the absorptivity, b is the pathlength of absorption, and c is the concentration of the absorbing species.
It thus can be seen that under suitable conditions, absorbance is directly proportional to analyte concentration through Beer""s law. The concentration of the analyte can be determined from the absorbance value, which in turn is calculated from the ratio of measured radiation transmitted and measured radiation incident. In addition, a true absorbance value can be obtained by measuring a reference or blank media sample and taking the ratio of the radiant power transmitted through the analyte sample to that transmitted through the blank sample.
In some types of conventional sample testing systems, samples are transferred sequentially to one or more sample cells that are contained within the analytical instrument (e.g., spectrophotometer) itself. Samples are first taken from test vessels and, using sampling pumps, carried over sampling lines and through sampling filters. The samples are then transported to a UV analyzer, an HPLC system, a fraction collector, or the like. The analytical instrument may include a carousel that holds several sample cuvettes, such that rotation of the carousel brings each cuvette into position at the sample cell in a step-wise manner. The pulsing of the light source supplying the initial optical signal can be synchronized by control means with the rotation of the carousel.
Examples of UV-vis spectrophotometers are those available from Varian, Inc., Palo Alto, Calif., and designated as the CARY(trademark) Series systems. In particular, the Varian CARY 50(copyright) spectrophotometer includes a sample compartment that contains a sample cell through which a light beam or pulse passes. Several sizes of sample cells are available. In addition, the spectrophotometer can be equipped with a multi-cell holder that accommodates up to eighteen cells. A built-in movement mechanism moves the cells past the light beam.
In other recently developed systems, fiber-optics are being used in conjunction with UV scans to conduct in-situ absorption measurementsxe2x80x94that is, measurements taken directly in the sample containers of either dissolution test equipment or sample analysis equipment. Fiber optic cables consist of, for example, glass fibers coaxially surrounded by protective sheathing or cladding, and are capable of carrying monochromatic light signals. A typical in-situ fiber-optic method associated with dissolution testing involves submerging a dip-type fiber-optic UV probe in test media contained in a vessel. A light beam (UV radiation) provided by a deuterium lamp is directed through fiber-optic cabling to the probe. Within the probe, the light travels through a quartz lens seated directly above a flow cell-type structure, the interior of which is filled with a quantity of the test media. The light passes through the test media in the flow cell, is reflected off a mirror positioned at the terminal end of the probe, passes back through the flow cell and the quartz lens, and travels through a second fiber-optic cable to a spectrometer.
For the previously described Varian CARY 50(trademark) spectrophotometer, a fiber-optic dip probe coupler is available to enable in-situ sample measurement methods and effectively replace the need for a sipper accessory. This fiber optic coupler can be housed in the spectrophotometer unit in the place of the conventional sample cell. The coupler includes suitable connectors for coupling with the source and return optical fiber lines of a remote fiber-optic dip probe. The light beam from the light source of the spectrophotometer is directed to the source line of the dip probe, and the resulting optical signal transmitted back to the spectrophotmeter through the return line.
Fiber optics have also been employed in connection with sample-holding cells. For example, U.S. Pat. No. 5,715,173 discloses an optical system for measuring transmitted light in which both a sample flow cell and a reference flow cell are used. Light supplied from a light source is transmitted through an optical fiber to the sample flow cell, and also through a second optical fiber to the reference flow cell. The path of transmitted light from each flow cell is directed through respective optical fibers toward an optical detector, and is controlled by an optical path switcher in the form of a light selecting shutter or disk.
It is acknowledged by persons skilled in the art that, when working with an array of flow cells, sample cells, cuvettes, probes, and other instruments of optical measurement, and particularly in connection with fiber-optic components, there remains a need for efficiently and effectively routing or distributing light energy to and from such sample containers. This need has been the subject of some developmental efforts.
For instance, U.S. Pat. No. 5,526,451 discloses a fiber-optic sample analyzing system in which a plurality of cuvettes each have a source optical fiber and a return optical fiber. A device is provided for selecting a source fiber to receive radiation for passage through a selected sample of one of the cuvettes, and for returning transmitted radiation from the selected cuvette through a selected return fiber to a spectrophotometer. The selection device includes a single rotatable retaining member supporting the respective ends of eight fiber-optic input lines and eight corresponding fiber-optic output lines. The respective ends of the fiber-optic lines are arranged in a ring around the central axis of the retaining member. The eight input lines define one half of the ring while the eight output lines define the other half. By this arrangement, each input line end affixed to the retaining member has a corresponding output line end affixed in diametrically opposite relation along the ring. Rotation of the retaining member determines which pair of input and output lines are respectively aligned with an input lens and an output lens disposed in spaced relation to the retaining member. A source beam passes through the input lens and into the selected input line at the end supported by the retaining member. The source beam then travels through the input line and into the sample cuvette associated with that particular input line. From the sample cuvette, the transmitted beam travels through the output line associated with the selected input line and sample cuvette. This output line terminates at its end supported by the retaining member. Since this output end is aligned with the output lens spaced from the retaining member, the transmitted beam passes through the output lens and is conducted to the analyzing means of the spectrophometer.
U.S. Pat. No. 5,112,134 discloses a vertical-beam photometric measurement system for performing enzyme-linked immunoabsorbent assay (ELISA) techniques. The system includes a light coupling and transmission mechanism utilizing a cylindrical rotor and a fiber-optic distributor. The mechanism receives light from a light assembly. The cylindrical rotor includes an optical fiber having an input end located at its center and an output end located near its periphery. As the rotor rotates, the input end of the fiber of the rotor remains stationary with respect to the light assembly, while the output end moves around a circular path. The light output of the fiber of the rotor is received by a fiber optic distributor containing a multiplicity of optical fibers having their respective input ends arranged in a circular array. As the rotor is indexed about its axis, the output end of its fiber can be brought into alignment with successive fibers of the distributor. On the output side of the distributor, the multiplicity of fibers lead to a fiber manifold. The manifold aligns each fiber with a corresponding one of an array of assay sites. A detector board is located below the assay sites. The detector board contains an array of photodetectors corresponding to the array of assay sites. Light from a selected fiber passes through a corresponding assay site, and into a corresponding photodetector of the detector board.
As in other systems, this system requires a plurality of photedetectors and is not capable of routing the incident light from each sample well to a single detection means.
U.S. Pat. No. 6,151,111 also discloses a vertical-beam photometric system in which a plate carrier sequentially advances an 8xc3x9712 microplate through a measurement station. Each column of eight wells is scanned by light emitted from a bundle of eight corresponding distribution optical fibers. Light supplied from a light source passes through a monochromator to a rotor assembly. Each of the eight distribution fibers enables light from the rotor assembly to be sequentially directed by a corresponding mirror vertically through a corresponding aperture, lens, and microplate well, and subsequently into a corresponding photodetector lens. The rotor assembly consists of two mirrors positioned so as to bend light received by the rotor assembly 180 degrees, after which the light can be directed into one of the distribution fibers. The rotor can then be moved into alignment with another distribution fiber.
U.S. Pat. No. 4,989,932 discloses a multiplexer for enabling the sampling of a number of different samples. The multiplexer contains a stationary cylindrical outer body and a rotatable optical barrel disposed within the outer body. A primary inlet port is located on one side of the outer body through which light is introduced into the multiplexer. A primary exit port is located on an opposing side of the outer body through which light exits the multiplexer for transmission to an apparatus for optically analyzing a sample. Pairs of ancillary inlet and exit ports are disposed around the cylindrical wall of the outer body, and are oriented radially (or transversely) with respect to the longitudinal axis. The rotatable barrel contains a first mirror and lens associated with the ancillary exit ports, and a second mirror and lens associated with the ancillary inlet ports. A stepper motor is used to rotate the barrel to successively align the mirrors and lenses with a selected pair of ancillary inlet and exit ports. Light transmitted through the primary inlet port along the longitudinal axis of the multiplexer is turned at a right angle by the first mirror, passes through the first lens, and exits the multiplexer through the selected ancillary exit port. From the selected ancillary exit port, the light is transmitted through a fiber-optic bundle to a sample and returns to the multiplexer through the corresponding selected ancillary inlet port. From the selected ancillary inlet port, the light passes through the second lens, is turned at a right angle by the second mirror, and exits the multiplexer along the longitudinal axis. Other pairs of ancillary inlet and exit ports can be selected by rotating the barrel. In another embodiment disclosed in this patent, incoming light is received by an optical rod that has an angled mirrored surface at its end. Rotation of the rod by a stepper motor positions the angled mirrored surface to direct the light into a selected fiber-optic bundle.
U.S. Pat. No. 5,804,453 discloses a system in which a fiber-optic biosensor probe is inserted into a test tube. The probe receives a light beam from a light source and sends a testing signal to the photodetectors of a spectrometer. Time division multiplexing and demultiplexing are implemented to distribute light to and from several biosensors. Switching among inputs and outputs is controlled by an input control signal provided by an electronic clocked counter.
U.S. Pat. No. 5,580,784 discloses a system in which a plurality of chemical sensors are associated with several sample vials and arranged between a light source and a photodetector. Optical fibers are used to direct radiation into each sensor, as well as to direct emissions out from the sensors. A wavelength-tunable filter is combined with an optical multiplexer to direct radiation serially to each sensor through the fibers.
In view of the current state of the art, there is a continuing need for improved means for efficiently and effectively routing or distributing light energy to and from sample testing sites. It would be therefore be advantageous to provide a fiber-optic channel selection apparatus that utilizes movable and/or fixed mechanical components to effect indexing among several optical input and/or output channels in an efficient and controlled manner without the need for costly optics-based switching components. In particular, it would be advantagous to provide an apparatus that enables analysis of multiple samples using only a single light source and a single detection means. Such an apparatus should be designed to minimize light loss and be compatible with a wide range of optical-based measurement systems. The present invention is provided to address these and other problems associated with the prior art.
According to one embodiment of the present invention, an optical channel selection device comprises a rotary member and a first stationary member. The rotary member is rotatable about a central axis, and comprises a first end surface, a second opposing end surface, an outer lateral surface disposed between the first and second end surfaces, and an internal bore. The internal bore includes a first bore end and a second bore end. The first bore end registers with the first end surface at a radially offset distance from the central axis and the second bore end registers with the second end surface collinearly with the central axis. The first stationary member comprises a first annular section and a first end section. The first annular section is coaxially disposed around the outer lateral surface of the rotary member. The first end section having a plurality of circumferentially spaced first apertures axially adjacent to the first end surface of the rotary member. Each first aperture is disposed in the first stationary member at the radially offset distance. Each first aperture is selectively optically alignable with the first bore end through incremental rotation of the rotary member.
The device can be coupled to a suitable motor and transmission arrangement such as gearing to enable powered and controlled rotation of the first bore end of the internal bore.
The internal bore and one or more of the apertures of the device can contain optical fibers to enable the efficient transmission of light to, from and/or through the device.
The device can further comprise a second stationary member coaxially disposed around the outer lateral surface. The second stationary member has a second aperture axially adjacent to the second end surface in alignment with the second bore end.
The device can advantageously comprise bearings interposed between the rotary member and the stationary members. Preferably, the bearings are the roller type.
According to another embodiment of the present invention, an optical channel selection device comprises a barrel, an internal optical fiber disposed within the barrel, a first bearing coaxially disposed around the barrel, and a first bearing sleeve coaxially disposed around the first bearing. The barrel is rotatable about a central axis, and comprises a first end surface and a second opposing end surface. The internal optical fiber includes a first fiber end and a second fiber end. The first fiber end is exposed on the first end surface at a radially offset distance from the central axis. The second fiber end is exposed on the second end surface collinearly with the central axis. The first bearing sleeve has a plurality of first bearing sleeve apertures circumferentially spaced from each other. Each first bearing sleeve aperture is disposed in the first bearing sleeve at the radially offset distance, and is selectively optically aligned with the second fiber end through incremental rotation of the barrel.
The first bearing sleeve can advantageously include a first annular section contacting a radially outermost surface of the first bearing. In addition, the first bearing sleeve apertures can be formed in a first end section adjacent to the first end surface of the barrel. By this configuration, the first end section and the first annular section of the first bearing sleeve cooperatively form a first shoulder around the first end surface of the barrel.
The device can also comprise a second bearing coaxially disposed around the barrel and a second bearing sleeve coaxially disposed around the second bearing. The second bearing sleeve has a second bearing sleeve aperture aligned with the second fiber end.
A single bearing that is axially long enough to engage both the first and second bearing sleeves could serve the function of the first and second bearings.
The present invention can be advantageously integrated in a mechanical, rotary fiber-optic multiplexer (and demultiplexer) apparatus for selecting channels through which a beam or pulse of light is routed in an indexing manner. The apparatus comprises one, two, or more rotary indexing devices provided in accordance with embodiments of the present invention. One of the rotary indexing devices demultiplexes a beam of light by distributing the light from a single, common outgoing or source line into a selected one of a plurality of outgoing or source channels. The selection is accomplished by rotating the demultiplexing device into a position at which the common outgoing or source line can optically communicate with the selected outgoing channel. The other rotary indexing device, when employed in the channel-selecting apparatus, multiplexes a beam of light for transmission into a single incoming or return line by selecting a selected one of a plurality of incoming or return channels. The selection is accomplished by rotating the multiplexing device into a position at which the common incoming or return line can optically communicate with the selected incoming or return channel. As an alternative to employing the multiplexing device, each incoming or return line can be optically aligned with a signal receiving means such as a photodetector, thereby eliminating the need for the second rotary indexing device and the common incoming or return line.
When two such rotary devices are provided, they can be mechanically interfaced so that rotation of one device concurs with rotation of the other device, with the result that the selection of a certain channel of the one device concurs with the selection of a corresponding channel of the other device. For instance, if each device includes twelve channels and thus twelve index positions, the selection of the channel at index position 1 of the one device simultaneously results in the selection of the channel at index position 1 of the other device.
According to an embodiment of the invention, each rotary device comprises two fixed components (i.e., first and second fixed components), a rotary component, and one or more bearings providing an interface between the fixed components and the rotary component. The rotary component is interposed between the two fixed components. Each fixed component faces a respective end of the rotary component. One of the fixed components (e.g., the first fixed component) has an optical aperture at its axial center. The other fixed component (e.g., the second fixed component) has a plurality of optical apertures oriented in a circular arrangement about its axial center. The number of optical apertures in the circular arrangement corresponds to the number of optical channels selectable by the apparatus of the invention. The rotary component has a light guiding path such as an optical fiber having one end located at the axial center of the rotary component and another end located radially outward with respect to the axial center. The centrally located end of the optical fiber of the rotary component is separated from the centrally located optical aperture of the first fixed component by a very small air gap. The offset end of the optical fiber of the rotary component is likewise separated from the plurality of optical apertures of the second fixed component by a very small air gap. These air gaps optimize light transmission while minimizing light loss, and avoid the necessity of using expensive additional optical components to couple the respective apertures and fiber ends of the fixed and rotary components. Indexed rotation of the rotary component with respect to the second fixed component results in selective coupling between the offset end of the optical fiber of the rotary component and each aperture of the second fixed component.
As indicated previously, the two rotary devices included with the channel selecting apparatus can be made to rotate together through a mechanical interface. This interface can be accomplished through a suitable set of gears arranged such that rotation of at least one gear results in rotation of both rotary devices. For example, each rotary device could be provided with its own gear, and each of these gears could be placed in meshing engagement with a third gear. While manual rotation of the third gear in order to rotate the other gears is possible, it is preferred that the third gear be powered through connection to a motor or similarly automated device. The motor could then be electronically controlled by suitable electronic hardware and/or software. As an alternative to providing gears with each rotary device, gear-like teeth could be formed on respective structures of the rotary devices to eliminate additional gearing. In either case, the rotary devices of the apparatus can be rotated continuously without the need to reverse rotation upon completion of the indexing of each channel provided. For instance, for a twelve-channel apparatus, the sampling interval from index position 1 to index position 2 is equivalent to the sampling interval from index position 12 to index position 1.
As an alternative, the first rotary device utilized to select an outgoing channel is provided, but the second rotary device utilized to select an incoming channel is eliminated in favor of suitably collecting a bundle of optical return fibers constituting the incoming channels at a fixed position at which the ends of the fibers are optically aligned with the receiving window of a optical detection device.
The invention as just described offers advantages when incorporated into any system that includes one or more light sources and one or more devices adapted for receiving light energy from the light sources. In such systems, the mechanical multiplexing/demultiplexing functions realized by the present invention are useful in networking one or more light signals from selected light sources to selected receiver devices. The invention also offers advantages when incorporated into any system that uses optics to route optical signals over several lines or channels between a single light source and a single detector. An example of this latter system is a UV-vis spectrophotometer, which is generally designed to conduct UV scans on prepared samples. It is often desirable to scan a multitude of samples. In accordance with the present invention, each sample can be held in a test vessel or a suitable cell or well, or in any other suitable sample holding or containment means, and fiber-optic input and output lines can be brought into operative communication with each sample test site, or with each probe associated with the sample test site. In this manner, each cell, probe, vessel or test site respectively becomes associated with one of the channels of the apparatus of the invention, and hence becomes associated with the corresponding index positions of the rotary device or devices of the apparatus. Accordingly, the selection of index position 1 of each rotary device, for example, corresponds to the selection of test vessel 1, cell 1, and so on.
The fiber-optic channel selecting apparatus can be directly integrated into the design of an optical-based sample measurement and/or analysis system or instrument, such as a spectroscopic apparatus. An example of a spectroscopic apparatus is a spectrophotometer.